U.S. patent application number 12/293016 was filed with the patent office on 2009-04-23 for dielectric ceramic composition.
This patent application is currently assigned to YOKOWO CO., LTD.. Invention is credited to Shi Luo, Takahiro Yamakawa.
Application Number | 20090105063 12/293016 |
Document ID | / |
Family ID | 38283276 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090105063 |
Kind Code |
A1 |
Luo; Shi ; et al. |
April 23, 2009 |
Dielectric Ceramic Composition
Abstract
There is provided a dielectric ceramic composition having a high
relative permittivity, a high frequency-quality factor, a small
absolute value temperature coefficient, a low sintering
temperature, and unreactivity with an internal conductor material.
The dielectric ceramic composition comprises a main component
represented by general formula
xZnOxNlb.sub.2O.sub.5yCaTiO.sub.3zCaO, wherein
37.ltoreq.x.ltoreq.50, 10.ltoreq.y.ltoreq.60, 3.ltoreq.z.ltoreq.40,
and x+y+z=100, and a boron (B) oxide as an accessory component in
an amount of 0.3 to 3.0 parts by weight in terms of B.sub.2O.sub.3
based on the main component.
Inventors: |
Luo; Shi; (Gunma-ken,
JP) ; Yamakawa; Takahiro; (Saitama-Ken, JP) |
Correspondence
Address: |
THE WEBB LAW FIRM, P.C.
700 KOPPERS BUILDING, 436 SEVENTH AVENUE
PITTSBURGH
PA
15219
US
|
Assignee: |
YOKOWO CO., LTD.
Tokyo
JP
|
Family ID: |
38283276 |
Appl. No.: |
12/293016 |
Filed: |
March 15, 2007 |
PCT Filed: |
March 15, 2007 |
PCT NO: |
PCT/JP2007/055929 |
371 Date: |
September 15, 2008 |
Current U.S.
Class: |
501/123 |
Current CPC
Class: |
C04B 2235/3208 20130101;
C04B 2235/656 20130101; C04B 2235/3409 20130101; C04B 35/62675
20130101; C04B 35/6263 20130101; C04B 2235/3236 20130101; H01G
4/1254 20130101; H01G 4/1227 20130101; C04B 2235/3251 20130101;
C04B 2235/3281 20130101; C04B 2235/3284 20130101; C04B 2235/604
20130101; C04B 35/495 20130101; C04B 35/465 20130101 |
Class at
Publication: |
501/123 |
International
Class: |
C04B 35/03 20060101
C04B035/03 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2006 |
JP |
2006-072440 |
Claims
1. A dielectric ceramic composition comprising: a main component
represented by general formula
xZnO.xNb.sub.2O.sub.5.yCaTiO.sub.3.zCaO wherein
37.ltoreq.x.ltoreq.50, 10.ltoreq.y.ltoreq.60, 3.ltoreq.z.ltoreq.40,
and x+y+z=100; and a boron (B) oxide as an accessory component in
an amount of 0.3 to 3.0 parts by weight in terms of B.sub.2O.sub.3
based on said main component.
2. The dielectric ceramic composition according to claim 1, which
further comprises a copper (Cu) oxide as an additional accessory
component in an amount of 0.05 to 5.0 parts by weight in terms of
CuO.
3. The dielectric ceramic composition according to claim 1, wherein
any X-ray diffraction peak derived from TiO.sub.2 does not appear.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dielectric ceramic
composition. More particularly, the present invention relates to a
dielectric ceramic composition having a high relative permittivity,
a high frequency-quality factor, a small absolute value temperature
coefficient of resonance frequency, and a low sintering
temperature.
BACKGROUND OF THE INVENTION
[0002] The development of information communication equipment such
as mobile communication equipment in recent years has led to an
increasing expectation for enhanced performance of dielectric
ceramics for microwave applications to meet property requirements
of such information communication equipment. Specifically, although
properties required of ceramic compositions for dielectric ceramics
vary depending upon applications, commonly required properties
include high relative permittivity for reducing the size of
devices, a high frequency-quality factor for suppressing
attenuation, a reduction in absolute value of temperature
coefficient of resonance frequency for improving the thermal
stability, and a low sintering temperature and unreactivity with an
internal conductor material for simultaneous firing of the ceramic
composition and the internal conductor material.
[0003] Under the above circumstances, ZnO--Nb.sub.2O.sub.5-based
compositions (Japanese Patent Laid-Open No. 37429/1995: patent
document 1 and U.S. Pat. No. 5,756,412: patent document 4) and
compositions comprising CuO, V.sub.2O.sub.5, and Bi.sub.2O.sub.3
added to the ZnO--Nb.sub.2I.sub.5-based composition (Japanese
Patent Laid-Open No. 169330/1995: patent document 2) have been
developed. Further, ZnO--Nb.sub.2O.sub.5--TiO.sub.2-based
compositions (Japanese Patent Laid-Open No. 44341/2000: patent
document 3) and ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3-based
compositions (Journal of the European Ceramic Society 23 (2003)
2479-2483: non-patent document 1) have also been developed.
[0004] These compositions, however, do not simultaneously satisfy
all the above property requirements. For example, some of the
conventional compositions had a large absolute value temperature
coefficient. Some other conventional compositions had a high
relative permittivity, a high frequency-quality factor, and a low
absolute value temperature coefficient, but on the other hand, they
required a high sintering temperature. Further, some other
conventional compositions had a low required firing temperature,
but on the other hand, they were reactive with silver which is
contemplated as an internal conductor material. The above
properties are mutually correlated with each other. Accordingly, an
enhancement in some properties results in deterioration of other
properties, and, thus, it has been difficult to produce a
composition simultaneously satisfying all the above property
requirements.
[0005] For example, the low-temperature sintered material disclosed
in non-patent document 1 is composed mainly of
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3, and a few accessory components
have been added as a firing aid to make it possible to fire the
material at a lower temperature. This material, however, is
reactive with silver and cannot be used as a material for
low-temperature fired laminated substrates where silver is used as
an internal conductor. A possible reason for this is that the main
component CaTiO.sub.3 is reacted with ZnO and Nb.sub.2O.sub.5 at a
high temperature to give TiO.sub.2 which is then disadvantageously
reacted with an internal conductor electrode.
DISCLOSURE OF THE INVENTION
[0006] In view of the above problems of the prior art, the present
invention has been made, and an object of the present invention is
to provide a dielectric ceramic composition having a high relative
permittivity, a high frequency-quality factor, a small absolute
value temperature coefficient, a low sintering temperature, and
unreactivity with an internal conductor material. A preferred
object of the present invention is to provide a dielectric ceramic
composition for microwave applications, which has a relative
permittivity of 19.1.ltoreq..di-elect cons.r.ltoreq.25.2, a
frequency-quality factor of 1680 to 10515 GHz, and a resonance
frequency temperature coefficient (Tcf) of -31.9 to +32.1
ppm/.degree. C., can be sintered at a temperature at or below the
melting point of an internal conductor formed of, for example, an
Ag--Pd-base (silver-palladium-base) alloy, an Ag--Pt-base
(silver-platinum-base) alloy, an Ag--Au-base (silver-gold-base)
alloy, an Ag--Cu-base (silver-copper-base) alloy, or a simple
substance of Ag, Cu or Au, and, at the same time, is not reactive
with these internal conductors.
[0007] The above object of the present invention can be attained by
a dielectric ceramic composition characterized by comprising: a
main component represented by general formula
xZnO.xNb.sub.2O.sub.5.yCaTiO.sub.3.zCaO, wherein
37.ltoreq.x.ltoreq.50, 10.ltoreq.y.ltoreq.60, 3.ltoreq.z.ltoreq.40,
and x+y+z=100; and a boron (B) oxide as an accessory component in
an amount of 0.3 to 3.0 parts by weight in terms of B.sub.2O.sub.3
based on said main component.
[0008] In a preferred embodiment of the present invention, the
dielectric ceramic composition further comprises a copper (Cu)
oxide as an accessory component in an amount of 0.05 to 5.0 parts
by weight in terms of CuO.
[0009] In another preferred embodiment of the present invention,
the dielectric ceramic composition does not exhibit any X-ray
diffraction peak derived from TiO.sub.2.
[0010] The dielectric ceramic composition according to the present
invention can simultaneously satisfy all the requirements of
relative permittivity, frequency-quality factor, and temperature
coefficient, can be sintered at a low temperature at or below the
melting point of Ag, Cu, or Au as a simple substance or an alloy
composed mainly of Ag, Cu, or Au, which is contemplated as an
internal conductor material, and can suppress the precipitation of
TiO.sub.2 crystals by virtue of the addition of CaO and does not
have any adverse effect, derived from a chemical reaction between
the internal conductor and TiO.sub.2, on the internal
conductor.
[0011] The dielectric ceramic composition according to the present
invention has an additional effect that it can be produced by a
simple process. Specifically, since the main component and the
accessory component can be calcined together, the production
process can be simplified as compared with the conventional process
in which an accessory component is added to a previously calcined
main component, and the mixture is then subjected to secondary
calcination. Further, the recovery of the dielectric ceramic
composition can be improved, and the cost can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an X-ray diffraction pattern of a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3-based composition which is a
conventional composition;
[0013] FIG. 2 is an X-ray diffraction pattern of a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3--CaO-based composition which is a
composition of the present invention;
[0014] FIG. 3 is a photomicrograph of a fine pattern formed on a
substrate by forming a silver conductor on a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3-based composition, which is a
conventional composition, firing the composition and the silver
conductor together, and then forming the fine pattern on the
substrate; and
[0015] FIG. 4 is a photomicrograph of a fine pattern formed on a
substrate by forming a silver conductor on a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3--CaO-based composition, which is
a composition according to the present invention, firing the
composition and the silver conductor together, and then forming the
fine pattern on the substrate.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Embodiments of the present invention will be described.
[0017] Dielectric Ceramic Composition
[0018] The dielectric ceramic composition according to the present
invention comprises a main component represented by general formula
xZnO.xNb.sub.2O.sub.5.yCaTiO.sub.3.zCaO and a boron oxide and
preferably a copper oxide as an accessory component. In the main
component, x, y and z satisfy the following relationship:
37.ltoreq.x.ltoreq.50, 10.ltoreq.y.ltoreq.60, 3.ltoreq.z.ltoreq.40
and x+y+z=100. The content of each accessory component based on 100
parts by weight of the main component is 0.3 to 3.0 parts by weight
for the boron oxide in terms of B.sub.2O.sub.3 and is 0.05 to 5.0
parts by weight for the copper oxide in terms of CuO which is
preferably added as an additional accessory component.
[0019] Property Requirements
[0020] The following properties are mainly required of the
dielectric ceramic composition according to the present
invention.
[0021] The dielectric ceramic composition according to the present
invention is mainly contemplated for use in applications of
electronic devices using an Ag--Pd-base alloy, an Ag--Pt-base
alloy, an Ag--Au-base alloy, an Ag--Cu-base alloy, or a simple
substance of Ag, Cu or Au as an internal conductor, and examples of
preferred applications include antennas, laminated filters, baluns,
duplexers, and laminated substrates. For some applications, the
dielectric ceramic composition may be used in combination with a
composition having a low relative permittivity.
[0022] In producing the above electronic devices comprising an
internal conductor, since simultaneous firing of the internal
conductor and the dielectric ceramic composition can render the
production process efficient, it is an important property that the
dielectric ceramic composition can be sintered at a temperature at
or below the melting point of the internal conductor. Specifically,
the sintering temperature is desirably 920.degree. C. or below,
preferably 900.degree. C. or below, more preferably 880.degree. C.
or below.
[0023] In general, when the relative permittivity (.di-elect
cons.r) is higher, the possible reduction level of the size of
electronic devices is larger. Accordingly, a high relative
permittivity is preferred. For example, when the dielectric ceramic
composition according to the present invention is used in
high-frequency dielectric filters, since the wavelength of the
filter depends upon the magnitude of the relative permittivity, a
larger relative permittivity is advantageous for reducing the size
of the filter. The frequency-quality factor, however, is generally
lowered as the relative permittivity is increased. Therefore, the
high relative permittivity is not always preferred unconditionally.
In the dielectric ceramic composition according to the present
invention, the relative permittivity value is not less than 19.1,
preferably not more than 25.2, more preferably not less than 20 and
not more than 25.
[0024] A lowering in frequency-quality factor (f.Q property) means
that the loss of the electronic device is increased. Accordingly,
the frequency-quality factor value should be not less than a
certain value. In the dielectric ceramic composition according to
the present invention, the frequency-quality factor is not less
than 1680 GHz, preferably not less than 1800 GHz, more preferably
not less than 4000 GHz.
[0025] The temperature coefficient of the resonance frequency (Tcf
or .tau.f; often referred to simply as "temperature coefficient")
means the degree of change in resonance frequency upon a
temperature change. Accordingly, it can be said that the thermal
stability enhances with reducing the absolute value of the
temperature coefficient. In the dielectric ceramic composition
according to the present invention, the temperature coefficient is
-31.9 to +32.1 ppm/.degree. C., preferably -30 to +30 ppm/.degree.
C., more preferably -20 to +20 ppm/.degree. C., still more
preferably -10 to +10 ppm/.degree. C.
[0026] In the present invention, the temperature coefficient
(ppm/.degree. C.) is calculated by the following equation:
Tcf=[(f85.degree. C.-f25.degree. C.)/f25.degree.
C.].times.1000000/60
wherein Tcf represents the temperature coefficient of relative
permittivity at 25.degree. C. to 85.degree. C.; f85.degree. C.
represents resonance frequency at 85.degree. C.; and f25.degree. C.
represents resonance frequency at 25.degree. C.
[0027] As described above, the dielectric ceramic composition
according to the present invention is mainly used, for example, for
applications of electronic devices using an alloy composed mainly
of Ag, Cu and Au as an internal conductor. To this end, it is
preferred to avoid adverse effect caused by interaction between the
internal conductor material and the dielectric ceramic composition,
for example, during sintering. That is, the compatibility of the
dielectric ceramic composition and the internal conductor material
in sintering is preferably good. Further, as described above, when
TiO.sub.2 crystals are present within the dielectric ceramic
composition, interaction occurs between TiO.sub.2 crystals and the
internal conductor material, disadvantageously resulting in the
disappearance of the internal conductor material upon sintering due
to a reaction between the internal conductor material and the
dielectric ceramic composition, or the diffusion of the internal
conductor material. Accordingly, the prevention of the interaction
between the internal conductor material and the dielectric ceramic
composition can be said to be the prevention of the precipitation
of TiO.sub.2 crystals.
[0028] FIG. 1 shows an X-ray diffraction pattern of a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3-based composition which is a
conventional composition. In FIG. 1, (a) represents an X-ray
diffraction pattern of a sinter of the dielectric material and (b)
represents an X-ray diffraction pattern of a sinter obtained by
simultaneously sintering the dielectric material and an internal
conductor material (silver). As can be seen from (a) in FIG. 1, an
X-ray diffraction peak of TiO.sub.2 in the sinter of the dielectric
material appears around 27 degrees, indicating that TiO.sub.2
crystals have been precipitated. On the other hand, as can be seen
from (b) in FIG. 1, in the X-ray diffraction pattern of the
co-sinter of the dielectric material and silver, the intensity of
the X-ray diffraction peak derived from TiO.sub.2 is very weak and
is nearly zero. This suggests that, upon the partial liberation of
TiO.sub.2 from the main component CaTiO.sub.3, the liberated
TiO.sub.2 is reacted with the silver conductor, resulting in a
reduction in the amount of the silver conductor.
[0029] FIG. 2 shows an X-ray diffraction pattern of a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3--CaO-based composition which is a
composition according to the present invention. In FIG. 2, (a)
represents an X-ray diffraction pattern of a sinter of the
dielectric material and (b) represents an X-ray diffraction pattern
of a sinter obtained by co-sintering the dielectric material and a
conductor (silver). As can be seen from (a) in FIG. 2, any X-ray
diffraction peak derived from TiO.sub.2 in the dielectric material
does not appear around 27 degrees, indicating that TiO.sub.2
crystals have not been precipitated. Further, as can be seen from
(b) in FIG. 2, also in an X-ray diffraction peak of the co-sinter
of the dielectric material and silver, any diffraction peak derived
from TiO.sub.2 in the dielectric material does not appear. In the
dielectric ceramic composition according to the present invention,
the precipitation of TiO.sub.2 crystals considered attributable to
the reaction between the electric ceramic composition and the
silver conductor could have been suppressed by the addition of a
given amount of CaO.
[0030] FIG. 3 is a microphotograph of a product produced by forming
a silver conductor on a ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3-based
composition, which is a conventional composition, and then holding
the assembly at 870.degree. C. for 2 hr for co-sintering of the
composition and the silver conductor. The microphotograph shows
that the silver conductor partially disappeared due to a reaction
between the silver conductor and the dielectric ceramic
composition, or the diffusion of the silver conductor.
[0031] FIG. 4 is a microphotograph of a product produced by forming
a silver conductor on a
ZnO--Nb.sub.2O.sub.5--CaTiO.sub.3--CaO-based composition, which is
a composition according to the present invention, and then holding
the assembly at 870.degree. C. for 2 hr for co-sintering of the
composition and the silver conductor. The microphotograph shows
that the silver conductor has remained unreacted with the
dielectric ceramic composition and the silver conductor has not
been substantially lost by the sintering.
[0032] Composition Range
[0033] Low-temperature sinterabiltiy, relative permittivity,
frequency-quality factor, temperature coefficient, compatibility
with an internal conductor and other properties are greatly
influenced by the composition of the main components in the
dielectric ceramic composition. In the dielectric ceramic
composition according to the present invention, the following
composition range is preferred.
[0034] At the outset, CaO functions to suppress the precipitation
of TiO.sub.2 crystals and thus to improve the compatibility of the
dielectric ceramic composition with the internal conductor, whereby
the reaction with the electrode and the diffusion of the electrode
within the dielectric material can be suppressed. When the content
of CaO, that is, z value, is less than 3% by mole, the temperature
coefficient is reduced toward a minus value side and, at the same
time, an X-ray diffraction peak derived from TiO.sub.2 appears.
That is, TiO.sub.2 crystals are precipitated and are reacted with
the conductor electrode, and, consequently, the material is
rendered unsuitable for electronic devices using an alloy composed
mainly of Ag, Cu and Au as an internal conductor. On the other
hand, when the content of CaO, that is, z, exceeds 40% by mole, the
temperature coefficient is significantly shifted toward a plus
value side and, at the same time, the frequency-quality factor is
lowered. A lowering in frequency-quality factor means an increase
in loss of the electronic device and thus is unfavorable.
Accordingly, the content of CaO is limited to such a range that can
ensure the frequency-quality factor. That is, the z value is 3 to
40% by mole, more preferably 7 to 300% by mole, still more
preferably 15 to 25% by mole.
[0035] When the content of ZnO and Nb.sub.2O.sub.5, that is, x, is
less than 37% by mole, the temperature coefficient is increased.
Accordingly, the content of ZnO and Nb.sub.2O.sub.5 is limited to
such a range that can ensure the temperature coefficient. On the
other hand, when the content of ZnO and Nb.sub.2O.sub.5, that is,
x, exceeds 50% by mole, an X-ray diffraction peak derived from
TiO.sub.2 appears. That is, TiO.sub.2 crystals are precipitated and
are reacted with the conductor electrode, whereby the material is
rendered unsuitable for use in electronic devices using an alloy
composed mainly of Ag, Cu and Au as an internal conductor. Further,
in this case, the temperature coefficient is unfavorably
significantly shifted toward a minus value side. For the above
reason, the x value is 37 to 50% by mole, more preferably 40 to 48%
by mole, still more preferably 42 to 47% by mole.
[0036] When the content of CaTiO.sub.3, that is, y, is less than
10% by mole, the temperature coefficient is unfavorably
significantly shifted toward a minus side. On the other hand, when
the content of CaTiO.sub.3, that is, y, exceeds 60% by mole, the
temperature coefficient is significantly shifted toward a plus
value side and, at the same time, TiO.sub.2 crystals are
disadvantageously precipitated and are reacted with the internal
conductor. For the above reason, the content of CaTiO.sub.3 is
limited to such a range that can ensure the small absolute value
temperature coefficient. That is, the y value is 10 to 60% by mole,
more preferably 20 to 50% by mole, still more preferably 30 to 40%
by mole.
[0037] The composition range of the accessory component in the
dielectric ceramic composition according to the present invention
is preferably as follows.
[0038] At the outset, when the content of the boron oxide is less
than 0.3 part by weight in terms of B.sub.2O.sub.3 based on the
main component, the low-temperature sintering effect attained by
the boron oxide is unsatisfactory. On the other hand, when the
content of the boron oxide exceeds 3.0 part by weight,
disadvantageously, a deterioration in dielectric properties such as
a lowered frequency-quality factor takes place. For the above
reason, the content of the boron oxide is 0.3 to 3.0 parts by
weight, more preferably 0.5 to 2.0 parts by weight, still more
preferably 0.6 to 1.6 parts by weight, in terms of B.sub.2O.sub.3
based on the main component.
[0039] Copper oxide may be added from the viewpoint of improving
the appearance of the product. When the content of the copper oxide
exceeds 5.0 parts by weight in terms of CuO based on the main
component, the frequency-quality factor is disadvantageously
lowered. For this reason, the content of the copper oxide is
preferably 0.05 to 5.0 parts by weight, more preferably 0.5 to 4.0
parts by weight, still more preferably 1.0 to 3.0 parts by weight,
in terms of CuO based on the main component.
[0040] Production Process
[0041] The production process of a dielectric ceramic composition
according to the present invention will be described.
[0042] At the outset, oxides of niobium, zinc and calcium and
calcium titanate are provided as main components. In this case,
oxides of calcium and titanium may be used as an original raw
material instead of calcium titanate. Further, boron oxide and
optionally copper oxide as accessory components are also provided.
They are weighed in predetermined amounts and are mixed together,
and the mixture is calcined. The main component and accessory
component materials may not be always oxides. The use of, for
example, carbonates, hydroxides, sulfides, and nitrides, which,
upon heat treatment in the air, can be converted to oxides, can
provide a dielectric ceramic composition equivalent to that in the
case where oxides are used.
[0043] The raw materials may be mixed together, for example, by wet
mixing using water or the like. Calcination is not indispensable,
and the dielectric ceramic composition according to the present
invention can be provided by firing. Preferably, however,
calcination is carried out, for example, from the viewpoint of
ensuring the homogeneity of the composition. Further, also when
carbonates or hydroxides are used as the raw materials, the
calcination is preferably carried out. In this case, for example,
calcination under conventional conditions of temperature about
700.degree. C. to 900.degree. C. and time a few hours suffices for
contemplated results.
[0044] When the calcination has been carried out, the particle size
of the resultant calcination product is large, and, thus,
pulverization of the calcination product to a predetermined
particle diameter to prepare a powder having a narrow particle size
distribution is preferred. This pulverization can also improve the
sinterability of the material.
[0045] The powder thus obtained can be formed into a sheet by a
conventional method, for example, doctor blading or extrusion. When
the dielectric ceramic composition and the internal conductor are
simultaneously sintered, a method may be adopted in which a
conventional conductor paste is printed on the sheet, lamination
pressing is carried out for integration, and the integrated
assembly is then fired. The firing is preferably carried out in an
oxygen-containing atmosphere such as air. The firing temperature
may be set to a value in the range of 850.degree. C. to 920.degree.
C. The firing time is preferably about 0.5 to 10 hr. Firing at the
above temperature for the above period of time can realize firing
at a low temperature at or below the melting point of Ag, Cu or Au
as a simple substance or an alloy composed mainly of Ag, Cu or Au.
Accordingly, electronic devices using a low-melting point metal
such as Ag, Cu or Au having low resistance as the internal
conductor can be realized.
[0046] In the present invention, the main component and the
accessory component may be simultaneously calcined. This can
simplify the production process as compared with the conventional
process in which an accessory component is added to a previously
calcined main component and the mixture is then subjected to
secondary clacination. Further, the recovery of the dielectric
ceramic composition can be improved, and the cost can be
reduced.
[0047] Since the dielectric ceramic composition according to the
present invention is free from environmental pollutants such as
PbO, Cr.sub.2O.sub.3 and Bi.sub.2O.sub.3, an environmental-friendly
low-temperature sintered dielectric material can be provided.
EXAMPLES
[0048] The following Examples further illustrate the present
invention.
[0049] ZnO, Nb.sub.2O.sub.5, CaCO.sub.3, and CaTiO.sub.3 were
provided as main component materials, and CuO and B.sub.2O.sub.3
were provided as accessory component materials. They were weighed
in such respective amounts that the mixing ratio among ZnO,
Nb.sub.2O.sub.5, CaCO.sub.3, CaTiO.sub.3, CuO and B.sub.2O.sub.3
after firing is as shown in the column of the main component
composition in Table 1 below. Pure water was added thereto to a
slurry concentration of 30%, followed by wet mixing in a ball mill
for 5 hr. The mixture was then dried. The dried powder was calcined
in the air at a temperature specified in Table 1 for two hr.
[0050] Pure water was added to the powder thus obtained to a slurry
concentration of 30%. The slurry was subjected to wet pulverization
in a ball mill for 24 hr, followed by drying to prepare a
dielectric material mixture.
[0051] Next, one part by weight of polyvinyl alcohol was added as a
binder to 100 parts by weight of each of the dielectric material
mixtures thus obtained. The mixtures were dried and were passed
through a mesh with an opening size of 150 .mu.m for
granulation.
[0052] The granule powder thus obtained was molded by a press
molding machine at a surface pressure of 1 ton/cm.sup.2 to prepare
cylindrical specimens having a size of 17 mm.phi. in
diameter.times.8 mm in thickness. The specimens were then fired in
the air at a temperature specified in Table 1 for 2 hr to prepare
dielectric ceramic composition samples.
[0053] The samples were polished to a cylindrical form having a
size of 13.5 mm.phi. in diameter.times.6.5 mm in thickness and were
measured for dielectric properties. The relative permittivity
(.di-elect cons.r) and the no-load Q were measured by a hollow-type
dielectric material resonator method. The measurement frequency was
4 to 6 GHz. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Reaction With x y z CuO B2O3 Calcination
firing f Q .tau. f internal mol % mol % mol % wt % wt % temp.
.degree. C. temp. .degree. C. .epsilon. r GHz ppm/.degree. C.
conductor Ex. 1 50 10 40 0 3 800 850 25.2 2469 32.1 Not reacted Ex.
2 46.2 50 3.8 2 1.5 800 870 19.8 6408 -28.2 Not reacted Ex. 3 46.2
50 3.8 0 2 800 900 20.7 7013 -25.7 Not reacted Ex. 4 46.2 30.8 23.1
2 1.5 800 900 19.1 9054 -31.9 Not reacted Ex. 5 45.5 31.4 23.1 2 1
800 900 20.2 10515 -12.3 Not reacted Ex. 6 45.5 28.4 26.1 2 1 800
900 19.7 8192 -17.6 Not reacted Ex. 7 46.5 27.4 26.1 2 1 800 900
19.2 8671 -25.9 Not reacted Ex. 8 44.7 31.4 23.9 2 1 800 870 20.3
9476 -8.5 Not reacted Ex. 9 44.7 31.4 23.9 2 1 800 900 20.8 9642
-1.5 Not reacted Ex. 10 44.7 31.4 23.9 2 0.8 800 870 20.7 9911 -2.7
Not reacted Ex. 11 44.7 31.4 23.9 2 0.8 800 900 20.9 9303 -3.1 Not
reacted Ex. 12 43.5 49.1 7.4 2 1.5 800 870 21.8 2442 -5.0 Not
reacted Ex. 13 43.1 31.4 25.5 2 1 800 870 21.7 4926 20.5 Not
reacted Ex. 14 43.1 35.3 21.6 2 1.5 800 870 21.4 5976 8.5 Not
reacted Ex. 15 43.1 35.3 21.6 2 1.5 800 880 21.7 5301 5.4 Not
reacted Ex. 16 43.1 35.3 21.6 2 1.5 800 900 21.7 4174 3.5 Not
reacted Ex. 17 43.1 35.3 21.6 2 1 800 870 21.6 6922 13.7 Not
reacted Ex. 18 43.1 35.3 21.6 2 1 800 900 21.8 6382 12.8 Not
reacted Ex. 19 43.1 35.3 21.6 2 1 850 870 21.6 7089 11.9 Not
reacted Ex. 20 43.1 35.3 21.6 2 1 850 900 21.8 6402 12.7 Not
reacted Ex. 21 43.1 35.3 21.6 2 1 900 870 21.5 6408 9.9 Not reacted
Ex. 22 43.1 35.3 21.6 2 1 900 800 21.9 5732 9.7 Not reacted Ex. 23
43.1 35.3 21.6 2 1.2 800 870 19.1 7056 6.7 Not reacted Ex. 24 43.1
35.3 21.6 2 1.2 800 900 21.3 7337 9.1 Not reacted Ex. 25 43.1 35.3
21.8 2 0.8 800 870 21.8 7527 9.6 Not reacted Ex. 26 43.1 35.3 21.6
2 0.8 800 900 22.1 7104 9.2 Not reacted Ex. 27 43.1 35.3 21.6 2 0.8
850 870 21.9 7951 9.1 Not reacted Ex. 28 43.1 35.3 21.6 2 0.8 850
900 22.2 7516 9.2 Not reacted Ex. 29 43.1 35.3 21.6 2 0.8 900 870
21.7 7690 8.5 Not reacted Ex. 30 43.1 35.3 21.6 2 0.8 900 900 22.1
7390 8.6 Not reacted Ex. 31 42 47.3 10.7 2 1.5 800 870 22.8 1800
14.9 Not reacted Ex. 32 37 60 3 5 0.3 800 920 23.6 1836 12.8 Not
reacted Ex. 33 37 60 3 5.5 0.3 800 920 23.3 1685 12.5 Not reacted
Comp. Ex. 1 43.1 54 2.9 2 1 800 870 21.8 2442 -5.2 Reacted Comp.
Ex. 2 48 10 42 2 0.8 800 900 32.5 1672 74.6 Not reacted Comp. Ex. 3
33 44 23 2 1.5 800 900 32.6 1377 166.3 Not reacted Comp. Ex. 4 87
10 3 2 1 800 900 20.2 22600 -69.3 Reacted Comp. Ex. 5 87 8 5 2 1
800 900 20.4 19200 -71.6 Reacted Comp. Ex. 6 35 62 3 5 0.3 800 920
24.2 1570 13.2 Not reacted Comp. Ex. 7 37 60 3 5 0.2 800 920 Not
densified Comp. Ex. 8 50 10 40 0 3.5 800 850 24.9 1388 35.8 Not
reacted Comp. Ex. 9 85 10 5 2 1 800 900 22.4 17000 -65.0 Not
reacted Comp. Ex. 10 60 10 30 2 1.5 800 870 19.1 13108 -55.1 Not
reacted Comp. Ex. 11 51.9 22.2 25.9 2 1.5 800 900 17.0 5898 -46.6
Not reacted Comp. Ex. 12 35 44 21 2 1.5 800 900 30.0 1993 131.0 Not
reacted
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